/*
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* DO NOT ALTER OR REMOVE COPYRIGHT NOTICES OR THIS FILE HEADER.
*
* This code is free software; you can redistribute it and/or modify it
* under the terms of the GNU General Public License version 2 only, as
* published by the Free Software Foundation. Oracle designates this
* particular file as subject to the "Classpath" exception as provided
* by Oracle in the LICENSE file that accompanied this code.
*
* This code is distributed in the hope that it will be useful, but WITHOUT
* ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or
* FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License
* version 2 for more details (a copy is included in the LICENSE file that
* accompanied this code).
*
* You should have received a copy of the GNU General Public License version
* 2 along with this work; if not, write to the Free Software Foundation,
* Inc., 51 Franklin St, Fifth Floor, Boston, MA 02110-1301 USA.
*
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package com.sun.imageio.plugins.tiff;
public class TIFFCIELabColorConverter extends TIFFColorConverter {
// XYZ coordinate or reference white (CIE D65)
private static final float Xn = 95.047f;
private static final float Yn = 100.0f;
private static final float Zn = 108.883f;
private static final float THRESHOLD = (float)Math.pow(0.008856, 1.0/3.0);
public TIFFCIELabColorConverter() {}
private float clamp(float x) {
if (x < 0.0f) {
return 0.0f;
} else if (x > 100.0f) {
return 255.0f;
} else {
return x*(255.0f/100.0f);
}
}
private float clamp2(float x) {
if (x < 0.0f) {
return 0.0f;
} else if (x > 255.0f) {
return 255.0f;
} else {
return x;
}
}
public void fromRGB(float r, float g, float b, float[] result) {
float X = 0.412453f*r + 0.357580f*g + 0.180423f*b;
float Y = 0.212671f*r + 0.715160f*g + 0.072169f*b;
float Z = 0.019334f*r + 0.119193f*g + 0.950227f*b;
float YYn = Y/Yn;
float XXn = X/Xn;
float ZZn = Z/Zn;
if (YYn < 0.008856f) {
YYn = 7.787f*YYn + 16.0f/116.0f;
} else {
YYn = (float)Math.pow(YYn, 1.0/3.0);
}
if (XXn < 0.008856f) {
XXn = 7.787f*XXn + 16.0f/116.0f;
} else {
XXn = (float)Math.pow(XXn, 1.0/3.0);
}
if (ZZn < 0.008856f) {
ZZn = 7.787f*ZZn + 16.0f/116.0f;
} else {
ZZn = (float)Math.pow(ZZn, 1.0/3.0);
}
float LStar = 116.0f*YYn - 16.0f;
float aStar = 500.0f*(XXn - YYn);
float bStar = 200.0f*(YYn - ZZn);
LStar *= 255.0f/100.0f;
if (aStar < 0.0f) {
aStar += 256.0f;
}
if (bStar < 0.0f) {
bStar += 256.0f;
}
result[0] = clamp2(LStar);
result[1] = clamp2(aStar);
result[2] = clamp2(bStar);
}
public void toRGB(float x0, float x1, float x2, float[] rgb) {
float LStar = x0*100.0f/255.0f;
float aStar = (x1 > 128.0f) ? (x1 - 256.0f) : x1;
float bStar = (x2 > 128.0f) ? (x2 - 256.0f) : x2;
float YYn; // Y/Yn
float fY; // 'F' value for Y
if (LStar < 8.0f) {
YYn = LStar/903.3f;
fY = 7.787f*YYn + 16.0f/116.0f;
} else {
float YYn_cubeRoot = (LStar + 16.0f)/116.0f;
YYn = YYn_cubeRoot*YYn_cubeRoot*YYn_cubeRoot;
fY = (float)Math.pow(YYn, 1.0/3.0);
}
float Y = YYn*Yn;
float fX = fY + (aStar/500.0f);
float X;
if (fX <= THRESHOLD) {
X = Xn*(fX - 16.0f/116.0f)/7.787f;
} else {
X = Xn*fX*fX*fX;
}
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